Pseudoparalysis

Definition And Conceptual Framework

Pseudoparalysis refers to a state of apparent immobility or painful refusal to move a limb without true motor unit disease.
It is characterised by bizarre or unusual postures, diminished resistance of joints to passive movement, increased range of movement, paucity of spontaneous movements, and motor delay.
True paralysis results from a structural or functional lesion within the motor unit (anterior horn cell, peripheral nerve, neuromuscular junction, or muscle).
Pseudoparalysis must be differentiated from true neuromuscular weakness by evaluating for actual muscle weakness, wasting, fasciculations, altered deep tendon reflexes, sensory changes, or fatigability.
Non-neuromuscular causes of limb immobility, such as pain, fracture, severe infection, or systemic illness, are classical precipitants of pseudoparalysis-like states.

Determine the age at onset, mode of onset, and rapidity of disease progression.
Recurrent pneumonias and feeding problems serve as clues for a true neuromuscular disorder.
Antenatal history of decreased fetal movements and polyhydramnios suggests a true motor unit defect, notably Spinal Muscular Atrophy (SMA).
Review perinatal history for birth weight, hypoxia, or sepsis.
Assess developmental history; motor delay with preserved intellectual development implies a true motor unit defect rather than apparent paralysis.

Observe posture; a frog-leg position in severe SMA indicates profound true weakness.
Evaluate alertness; infants with SMA type 1 remain highly alert despite profound true weakness.
Perform the axillary suspension test; a truly hypotonic infant will slip through the examiner's hands.
Assess for tongue fasciculations, which denote a neuropathic origin and true paralysis.
Determine if weakness is proportionate to hypotonia; proportionate weakness indicates muscle or nerve aetiology, while disproportionate weakness suggests a central, systemic, or metabolic cause.
Evaluate deep tendon reflexes; brisk reflexes point towards an upper motor neuron cause like hypotonic cerebral palsy.

Feature	Central Hypotonia	Peripheral Hypotonia (True Paralysis)
Level of Lesion	Proximal to anterior horn cell	Motor unit
Muscle Tone	Reduced	Reduced
Deep Tendon Reflexes	Normal or brisk	Depressed or absent
Degree of Weakness	Mild (+)	Severe (++)
Antigravity Limb Movements	Present	Absent
Contractures/Deformities	Absent	Usually present
Seizures/Dysmorphism	May be present	Absent

AFP is defined as rapid onset weakness progressing to maximum severity within days to weeks.
Pseudoparalysis-like states, characterised by painful disuse without true flaccid paralysis, must be excluded through a lack of true motor unit signs.
True AFP must be differentiated from conditions presenting as apparent immobility.

Feature	Poliomyelitis	Guillain-Barré Syndrome	Transverse Myelitis	Traumatic Neuritis
Fever	May be biphasic	May have prodromal	May have prodromal	Absent
Symmetry	Asymmetric	Symmetrical	Symmetrical	Asymmetric
Sensations	Intact; diffuse myalgias	Variable	Impaired below level	Impaired in affected nerve distribution
Respiratory Insufficiency	May be present (bulbar)	May be present	May be present	Absent
Cranial Nerves	May be affected	May be affected	Absent	Absent

Central causes of hypotonia and apparent weakness, such as acute illness, asphyxia, bilirubinemia, and metabolic errors, must be excluded first.
The presence of paradoxical respiration and a bell-shaped chest are characteristic of true neuromuscular weakness, specifically SMA.
Contractures present at birth suggest arthrogryposis, denoting true in-utero paralysis due to severe congenital muscular dystrophy or myopathy, definitively ruling out acquired pseudoparalysis.